中文摘要：

以杭州原状软土为研究对象，借助扫描电镜和PCAS微观定量测试技术，采用分形理论对波浪荷载下的饱和软土微观结构进行研究，探讨不同循环应力比和不同频率条件下孔隙的分布特征及其变化规律。结果表明：循环应力比越大或频率越低，试样破坏所需的循环次数越少；试样临界破坏应变水平随循环应力比的增加呈升高趋势，而不同频率下的临界破坏应变水平则基本一致；孔隙的尺度、排列、形态等特征均随循环应力比的变化呈规律性变化，但随频率变化没有明显的规律性；循环剪应力作用下，孔隙破碎的同时兼并生长，这是剪切带上褶皱现象的微观本质，并且孔隙排列方向与剪切带方向基本一致。通过循环加载前、后微观结构特征参数的变化规律，揭示了波浪荷载下循环应力比和频率对土体微观结构的影响以及土体宏观变形的微观机制。

英文摘要：

The fractal theory is used to study the microstructure of Hangzhou intact clay under wave loading by scanning electron microscope （SEM） and PCAS quantitative testing technology. The characteristics and variation of pores distribution under different cyclic stress ratios and different frequencies are investigated. The study results show that fewer cycles are required at higher stress ratio or lower frequency when the specimen approached failure. The levels of critical failure strain tend to increase with the increasing of cyclic stress ratio, but almost the same under different frequencies. The characteristics of pore distribution such as scale, arrangement and pattern would change regularly with the cyclic stress ratio;but no apparent regularity varies with frequency. Both contraction and dilatation exist on the shear band, caused by the pores which are broking while merging at the same time under cyclic shear stress;also, the pore’s orientation is consistent with the shear band’s direction. According to the variation of microstructure characteristic parameters before and after cyclic loading, the effects of cyclic stress ratio and frequency on microstructure of soft clay under wave loading are revealed;and the microscopic mechanism of wave loading is disclosed.